With increased focus on vehicle economy, automotive manufacturers are turning to smaller, lighter vehicles and unique vehicle powertrains to boost efficiency. Recirculated exhaust gas (“EGR”) is utilized in most conventional internal combustion engines to assist in the reduction of throttling losses at low loads, and to improve knock tolerance and reduce the level of oxides of nitrogen (“NOx”) in the exhaust gas. EGR is especially important as an emissions reducer in internal combustion engines that run lean of stoichiometry and are, as such, prone to emitting higher levels of NOx emissions.
One proposition that has been considered in the construction of internal combustion engine systems is to utilize one, or a plurality of cylinders as a dedicated EGR source. Specifically, in a four cylinder engine for instance, two or three of the four cylinders will run at normal air, fuel and EGR mixtures (working cylinders). The exhaust gas produced by these cylinders will exit the internal combustion engine as exhaust gas and be treated in an exhaust gas treatment system prior to its release to the atmosphere. One or two of the four cylinders is operated at customized levels of air and fuel (EGR cylinders); as may be determined by an engine controller that is in signal communication with various engine, vehicle and exhaust system sensors. The exhaust gas produced in these cylinders is transferred to the intake ports of the other cylinders to provide EGR. Such a configuration allows for richer EGR, which contains higher levels of Hydrogen, thereby improving knock resistance, fuel consumption and combustion stability while still allowing stoichiometrically combusted exhaust gas to be maintained in the exhaust gas treatment system for compatibility with the catalytic treatment devices.
A challenge is to deliver uniform volumes of EGR to the intake manifold upstream of a compressor, such as an engine driven supercharger or an exhaust driven turbocharger, to thereby promote an even distribution and mixing of the exhaust gas with combustion air for delivery of a homogeneous combustion charge to the working cylinders over a broad range of operating conditions.